The overall objective of this project is to investigate hormonal influences on the development of verbal fluency, speech production, reading and reading disability in non-disabled and disabled children as they mature. The focus of this study is on biologic mechanisms, specifically the influence of estrogen, on the development of reading skills over the course of puberty. Advances in our understanding of 1) the neurobiology of brain development; 2) the relationship between gonadal hormones and cognitive function and 3) the relationship between reading and language converge to suggest that there is a relationship between the rise of gonadal hormones and the development of reading skills between ages 7.5-17 years. In particular, data indicating that the component of language most implicated in reading and reading disability, phonological processing, also represents the area of verbal ability reported to be most sensitive to the effects of estrogen, support the notion that estrogen may influence the development of reading during the course of puberty. A cross-sequential longitudinal design, drawing upon three populations of children studied at ages which bridge prepuberty to late puberty, and to be sensitive to estrogen, and of reading ability are systematically administered every six months for 42 months while concurrently obtaining hormonal and physical indices of puberty fully maximize our ability to test our hypotheses and address the Specific Aims of the proposal.